The most common technique for forming a lens has been a method using polishing as disclosed in patent Literature 1 for example. Patent Literature 1 discloses a method for designing in advance a polishing plate to have a shape opposite to that of a lens to be formed, pressing the polishing plate to a glass material, and polishing the glass material by the polishing plate while supplying abrasive particles between the polishing plate and the glass material.
Further, with the increasing need for higher performance of optical systems, the technique of forming a non-spherical lens as well as the technique of processing a lens with high accuracy is getting more important. However, the polishing method disclosed in Patent Literature 1 has difficulty in forming a non-spherical lens. Therefore, it is necessary to combine a plurality of lenses in order to correct various optical aberrations such as a spherical aberration, a coma aberration, and astigmatism. This raises a problem of high production cost.
In order to deal with this problem, Patent Literature 2 for example discloses a hybrid lens which is obtained by attaching a resin layer to a glass lens base material and which has a large difference between the minimum and the maximum thickness of the lens and a large area of a non-spherical surface. FIG. 16 is a cross sectional view illustrating a hybrid lens 200 described in Patent Literature 2. The hybrid lens 200 has a configuration in which a resin layer 203 whose outer shape is non-spherical is attached to one side or both sides of a spherical glass lens base material 202. The spherical glass lens base material 202 may be a convex lens or a concave lens. The maximum thickness Tmax of the resin layer 203 within an effective diameter of the lens ranges from 1 mm to 10 mm, and preferably from 2 mm to 8 mm. Thus, the hybrid lens 200 has the thick resin layer 203, has a large difference between the minimum and the maximum thickness of the lens, and has a large area of a non-spherical surface.